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What is density
Density is how compact an object is
what is the formula for density
mass/ volume
What are the unit for density
kg/mÂł
How does density of a object determine if it floats or sinks in a fluid
solid object will float in liquid if it density is lower than that of the liquid
what is the density of water
1g/mÂł
What is hooke’s law
Extension is proportinal to the force applied
F= ke where k is springs constant
What are the units for springs constant
N/m
What is limit of proportionality
The limit beyond which hooke’s law is no longer obeyed
graph starts to curve 
WHat is the elastic limit
If you exceed this limit object won’t return to original lenght after its unloaded
Deformation
Force expericed by object cause change in shapt
tensile forces strech the shap
compressive forces compress the shape
What is elastic deformation
Material can still return to original length once unloaded, below elastic limit
What is plastic deformation
Material can’t still return to original length once unloaded
Why does plastic deformation happen
when force is applied some atom in material move positions relative to one another when the load is removed they don’t return to their original space
What from is the energy transferred to when elastically stretched or compressed
elastic strain energy = into kinetic or thermal energy
What from is the energy transferred to when plastically stretched or compressed
work is done to separate atoms so energy is stored in elastic strain energy
How does plastic deformation help in car crashes
Energy is transferred to change the shape of the vehicle rather than to the person
How do you calculate extension in parallel spring
extension in string/ number of springs
How do you calculate extension in parallel spring
F=nkL
How do you calculate extension in series spring
number of springs* extension of 1 spring
How do you calculate k in parallel spring
k1+k2 +k3…..+kn=Kt
How do you calculate k in series spring
1/k1 +1/k2 1/k3 +…..= 1/Kt
what does the area under force extenstion graph represnt
work done to strech/ compress= elastic strain enrgy
What is elastic strain energy
Ep+ thermal energy
What is stress defined as
force applied / crossedtional area
What are the units for stress
Pa or Nm^-2
What is strain
change is lenght / original lenght
What are the units for strain
no units as its a ratio
What happens at breaking point
the stress on material is so greate heat is causes the atoms to be pulled apart unitl they are sperated completly and material breaks
What is UTS
maximum stress a material can withstand - after this point no more extra force is applied but object will keep extending
What do can affect breaking point and UTS
temperature
What is young’s modulus
Its a measure of stifness
What does the gradient of stress strain graph show
Youngs modulus but only till stress is proportional t strain
What does the area under stress strain graph represent
Elastic strain energy per unit volume
What does ductile mean
how easy it is to draw out a material into a wire
what does brittle mean
object that break without bending or steching much
What is Yield point
- material suddenly starts to strech without extra load
What is the diffrence between force extension graphs vs stress strain graph
force extension graph are specifice to object
stress strian graph are specific to material
Note 
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